The field of 'human factors' (also known as ergonomics) is related to the study of how people interact physically and psychologically with particular environments, products, or services.
In the case of Web usability, we will discuss how people interact with Web sites.
What are Human Factors?
Human factors (also known as ergonomic) is the study of how humans behave physically and psychologically in relation to particular environments, products, or services.
Many large companies use inhouse, or outsourced, Human Factors experts to study how a new product will be accepted by the users that it is designed for. Usability is often used as an alternative to human factors, although human factors is really a larger area of study.
A typical human factors study is similar to a usability study, where a group of test subjects, representing future end users, are given tasks to do with a working prototype of a product.
The test subjects are observed and videotaped while doing a task, and asked to speak out any problems or observations they encounter. They are also interviewed after each test.
Depending on objectives, the result of a human factors study can include suggestions on how to improve a product design or general guidelines for designing such a product.
How Do We Use the Web?
Have you ever thought about how you surf the Web? It's actually like a combination of three common human activities:
We Scan Web Pages
Web users usually scan new pages they visit. They only read Web pages in full when they have found exactly what they are looking for. Who has time to read everything?
Why Do Humans Scan Web Pages?
We scan web pages because we want to find what we are looking for as quickly as possible. After all, life is short!
It is second nature to us - everyday we scan things before deciding whether we want to pursue it further. We scan people (admit it!), TV channels, radio stations, newspapers, magazines, books, and reports.
The human brain doesn't have the capacity to absorb every piece of information that bombards it every day. Scanning is the brain's mechanism of filtering the important information from the junk.
Humans usually select the first reasonable option (a strategy known as "satisficing" - a cross between "satisfying" and "sufficing").
We hardly ever select the best option from all available options. Our brain just can't be bothered to think all the time.
Why Do We Satisfice?
We satisfice because we want to reach our goal with minimum wasted effort and time.
There is little upside to spending time and effort to find the best option. If we make the wrong choice, which happens all the time, we can simply click the "Back" button on the browser and try again.
We Wander Through Things
Humans are lazy beings. We usually use things without figuring out how they should be used. On the purchase of a new VCR, how many people sit down and methodically read the whole book before turning it on? Infact, we often only turn to manuals when we actually get stuck!
Why Do We Wander Through Things?
We wander through things because we usually can't be bothered to waste time trying to learn how to use something properly. With our busy lives, who has the time? We are always in a hurry and don't care for how things work. As long as we can get something to work, we stick with that method.
Our memory plays a vital role in the usability of a Web site. Experience with a Web site provides us with the knowledge of, and a sense of comfort with, a particular place or system. It enables us to use a Web site successfully every time we return to it with minimum wasted time and effort.
This is why it is most important that Web designers try to minimize the number and amount of changes to a Web site layout and navigation system. Yahoo!'s Web designers realized this important usability feature a long time ago. This is why their Web site has changed little in the last few years.
I have seen first hand how a change in a site's layout can seriously affect a user's ability to use it. I recommend that you avoid merging the content of one Web site with another and redirecting the old site's traffic to the new site's home page.
Existing users of the old site will find that all the knowledge gained has been rendered useless. A lot of users will use another site they are more familiar with, if the new site requires too much effort and time to learn to use.